A number of chemical food preservatives have been employed against molds (as well as bacteria and yeasts) including sodium benzoate, often used in soft drinks and acidic foods; sodium and calcium propionates used in breads, cakes and cheeses; sorbic acid used in cheeses, moist dog foods, fruit juices, wines, and some baked products; and chlorine compounds used as a germicidal wash for fruits and vegetables (Potter, N. N., Food Science, 4th ed., AVI, CT, 1986, pp. 160 to 161 and DeMan, J. M., Principles of Food Chemistry, Van Nostrand Reinhold, N.Y., 1980, pp. 412-413; these book excerpts, and the others and patents cited hereafter, are expressly incorporated herein in their entireties by reference). Generically, "preservatives" also include fumigants such as ethylene oxide and ethyl formate used to control microorganisms on spices, nuts and dried fruits, and sulfur dioxide and sulfites used in wines (ibid.).
In 1985, Anderson disclosed the use of a Propionibacterium to ferment whey, thereby providing a composition containing propionic acid that exhibited mycostatic activity (U.S. Pat. No. 4,497,833). The patent suggested that the composition might be useful in bread and other bakery products (column 1, line 20). However, propionic acid has a distinct, unpleasant taste and stimulates a gag or vomiting reflex at concentrations lower than other similar organic acids such as acetic acid or citric acid.
Some years later, Boudreaux and Matrozza suggested using a propionate salt such as sodium or calcium propionate, or a propionate salt provided by fermenting Propionibacterium shermanii and then neutralizing the culture, to inhibit bacterial growth in raw or processed meat products (U.S. Pat. No. 5,219,603). A bacteriocidal composition combining a propionate with a bacteriocin produced by a Pediococcus species was also suggested to have efficacy for the same purpose.
More recently, Ayres, et al., at Oregon State University suggested that food might be preserved using metabolites of propionibacteria other than propionic acid (U.S. Pat. No. 5,096,718). Though the patent included yeasts, bacteria, and molds as target microorganisms (column 4, lines 41 to 44) and the examples illustrated mold inhibition in a yogurt substitute (Example 18), apple cider (Example 19), reconstituted orange juice (Example 20), and sour cream (Example 21), the claims were directed to gram-negative bacteria control. Additionally, with the exception of sour cream which was cultured for 46 days before mold appeared in a product containing propionibacterial metabolites, most of the reported studies involved product incubation for only a few days up to a week. Conditions for long-term storage at room temperature, and storage of products that are not typically refrigerated, were not disclosed.
Continuation-in-part application U.S. Pat. No. 5,260,061 to Ayers, et al., was directed to yeast control using propionibacterial metabolites, but mentioned mold control at column 1, line 25, column 2, lines 40 to 53, and column 3, line 17 to column 4, line 21. However, the text confused propionic acid/propionates with other metabolites, and the claims only covered protection against yeast spoilage. And, like the parent case, conditions for long-term storage at room temperature of products with low to moderate relative humidity were not mentioned. Instead, the examples illustrated yeast inhibition in yogurt, yogurt substitutes, sour cream, and fruit juices.
A third related application, U.S. Pat. No. 5,635,484 to Ayers, et al., described a peptide produced by propionibacteria, chemical synthesis, or cloned gene expression that was useful in preventing and treating gram-negative bacterial infections. Though of low molecular weight and therefore belonging to a subcategory, the peptide was nonetheless considered a bacteriocin (column 15, lines 37 to 39). Exactly two weeks later, U.S. Pat. No. 5,639,659 to Barefoot and Grinstead issued. It also disclosed a bacteriocin from a Propionibacterium for controlling certain lactic acid bacteria that spoiled dairy products such as yogurt and cottage cheese by over-acidification. Mold control was not addressed.
Japanese patent publication Kokai No. 7-115950 (application no. 5-289749) also disclosed use of propionibacterial bacteriocins, but in combination with a variety of compounds, including organic acids and their salts, essential oils and plant components for preserving foods (translation page 1, claim 1). More-over, the disclosure employed the bacteriocin activity against gram-positive and listeria bacteria (translation page 6, last line to page 7, line 2), not yeasts and molds, and the adjunct ingredients were described as primarily increasing bacterial cell membrane permeability (see, for example, translation page 8, paragraph 2, line 3 and paragraph 4, line 6 and page 9, 3 lines from page bottom). The specification was primarily directed to meat and fish product storage (translation page 10, paragraphs 3 and 4), and the examples illustrated hamburger, a Japanese radish product, and pollock.
More recently, WO 98/16124 to King, et al., disclosed the inhibition of yeast and molds in food products other than hamburger having a pH of greater than 5.5, more preferably greater than 5.8, and most preferably greater than 6.0, using propionibacterial metabolites and a potentiator such as chelators, essential oils, or organic acids (page 3, lines 21 to 27, and page 8, lines 7 to 12). The longest reported mold inhibition in a food product after storage at room temperature was after 28 days in coffee cakes (Example 1). The only other food product illustrated was a cheesecake stored refrigerated for six weeks (Example 2). The other examples reported data about mold and yeast growth in an in vitro incubation of potato dextrose broths for 48 hours (Example 3), 5 days (Example 4), and 7 days (Example 5).
It would be desirable to have improved compositions for the long-term preservation of food products stored at room temperature, especially packaged bakery products that have a tendency to develop mold growth. This is a particular problem with moist baked goods, especially those containing fruit such as figs, which are often contaminated with "smut", typically caused by spores of Aspergillus niger that are often difficult to detect on the fruit or in fruit ingredients such as pastes used in the manufacture of baked goods. In addition, some stored fruit-containing bakery products, especially those containing sugar in a fruit phase, if subjected in transit or storage to heat, tend to leak syrup that can exacerbate mold growth.